You can make the folders and other icons on your desk top fit your own personality. For instance, you can have the hard drive icon be the icon of your particular type of computer rather than the generic hard drive icon. Or you can color code the folders. Or you can have all your folders set in a theme such as Star Trek. You can even use photos as icons. It is really easy to do.

The most time consuming part is conducting an Internet search for the folder or icon set that you want to use. You can usually find something you want for free, but you can also purchase sets if you wish.

Once you have your icon(s) selected follow these simple steps.

When working with an existing icon image such as a folder.
Choose the image you want to use, click on it once to select it, then choose copy from the Edit menu (or hit Command + C)
Find the folder you want to change. Click on it once and choose File > Get Info (or right click and choose Get Info)
An information window will open and in the top left of the window will be the current folder icon. Click on it once and choose Edit > Paste (or hit Command + V). The new icon image will replace the old one.

When working with a photo or other regular image.
Open the image using Preview or a graphics utility application such as Graphic Converter or Photoshop. You don’t have to adjust the size.
Follow the same steps as noted above.